Starting with Minecraft PE version 0.16.0 the weather can be changed during gameplay as long as cheats are enabled. There two commands which allow you to change the weather, toggledownfall and weather.
Changing the weather with the /toggledownfall command
The /toggledownfall command allows the user the ability to start precipitation if it is currently falling or to stop precipitation if it is not. The type of precipitation is based upon the biome, warm or cold. Learn more about changing the weather with toggledownfall.
Changing the weather with the /weather command
Using the /weather command, the user can not only set the type of weather but also the duration for that weather to persist. The types of weather that can be specified are clear, rain (or snow in cold biomes) and thunder (or thunder snowstorm in cold biomes). Learn more about changing the weather with the weather command.
- Minecraft Commands – WikiHow
Last Updated Nov 28, 2016